* only display the ``this page doesn't exist'' 404 if there is at
* least one permutation. Otherwise, we give an irrelevant 404 for
* users with no permutations.
*/
if ($this->nPermutations && $page >= $npages)
Page::show_404('Unable to find page ' . $page . ', there are only ' . $this->nPermutations . ' non-conflicting permutations, for a total of ' . $npages . ' pages.');